Currently, after a phone handset is fully charged with a wireless charger or a transmit TX pad, which is also called wireless charger pad, the charging pad is switched to a standby mode by a Receiver Integrated Circuit RX IC which is also referred as a handset wireless charger IC inside the handset. The handset loses connection to the TX pad because the RX IC inside the handset gets all the energy from TX pad. This will become an issue when a maintenance charging phase occurs since the handset does not know if it is still on the TX pad or not, after the charging process is complete. The SW is not able to show the correct User Interface indication when the handset will need to be charged again after the battery voltage of the handset drops below a recharging threshold.
Therefore, in one of the scenarios, once the battery is fully charged, and if the end user may still leave the phone on the wireless charger pad and the maintenance charging mode may be needed. The issue is how to distinguish the maintenance charging phase from initial charging in order to enable the correct user indications (battery full even if the maintenance charging is ongoing).
In some earlier solutions, the wireless charger receivers have not been switched to standby mode after the battery is full. Therefore, the RX IC inside the handset remains active or stays alive during all the time that the handset is on the TX pad or the wireless charger. The tradeoff is huge power consumption (˜1.5 W) without doing anything, which is a waste of energy for the handset. The normal wall adapters consume less than 50 mW when those are not loaded (battery full). Therefore, a consumption of ˜1.5 W in standby current is not acceptable in the long run—especially when the handsets are kept on the wireless charger for long periods over night or over weekend.
The reason of this lack of user interface friendly environment is that inbuilt wireless charging in handsets is still at its early stage and these kinds of issues are still to be addressed.